1. Field of the Invention
The present invention relates to a communication system using a sheet light guide, and particularly, to a light guide which is formed by containing light-scattering particles in a sheet optical medium and propagates light incident from one end surface thereof to the other end surface side while scattering the light by the particles.
Moreover, the present invention relates to the sheet light guide for use in the communication system.
2. Description of the Related Art
Heretofore, for example, as described in U.S. Pat. Nos. 5,548,670 and 5,542,017, a light guide has been known, which is formed by containing light-scattering particles in an optical medium such as polymethylmethacrylate (PMMA), and propagates light incident from one end surface thereof to the other end surface side while scattering the light by the particles.
Such a light guide is that which propagates light while repeatedly scattering the light by the particles in the optical medium as well as by means of the mechanism of total reflection at an interface between the surface along the light guide and a surrounding medium (air or cladding layer). Accordingly, in comparison with a light guide which propagates the light only by the mechanism of the total reflection, the light guide thus described has an advantage in that light having an intensity which is more uniform can be taken out at an end surface where light is emitted. For example, as described in U.S. Pat. No. 5,822,475, it is conceived, by utilizing this advantage, to apply such a type of light guide to the purpose of constituting an optical data bus (sheet bus). The optical data bus is that which is formed by use of a sheet optical medium, and in which one input unit for inputting an optical signal is coupled to one end surface thereof, and a plurality of output units are coupled to the other end surface, thus distributing the inputted optical signal as a common signal to the plurality of output units.
Moreover, for example, as described in Japanese Unexamined Patent Publication No. 11 (1999)-031035, as such an optical data bus, one has been also known, in which light-scattering portions are provided on a light-incident-side end portion of the sheet optical medium so as to correspond to respective signal light incident portions, and signal light scattered and branched by the light-scattering portions is propagated toward a light-emitting-side end portion of the optical medium.
The sheet light guide formed by containing the light-scattering particles in the sheet optical medium, which is described in U.S. Pat. No. 5,822,475, is also frequently used by connecting a plurality of optical fibers provided in parallel to the one and the other end surfaces in order to constitute a plurality of nodes.